Brown the beef with the onion and garlic in a large, nonstick skillet for 5 minutes over medium-high heat. Add the lettuce and tomatoes. Stir in the Greek seasoning, 2 teaspoons lemon juice, and the remaining 1/4 teaspoon lemon pepper. Cook until heated thoroughly for about 5 minutes.

Spread the yogurt sauce on each pita. Top with the beef mixture, lettuce, tomatoes, and feta cheese.